1. Field of the Invention
The present invention relates to powered valve actuators for remotely-controlled operation of valves and, more particularly, to actuators for handwheel-operated valves. This invention is an improvement of a powered actuator disclosed in co-pending U.S. Pat. application Ser. No. 08/012,935, filed Feb. 17, 1993 and entitled "Powered Actuator for Valve".
2. Description of the Prior Art
Powered valve actuators typically include a motor, which has a housing and a rotating output shaft, and which is coupled to the handwheel or rotating operating element of the valve to effect rotation thereof. In such powered actuators, it is also necessary to provide a coupling between the motor and the valve so that the torque generated by the motor output shaft can operate the valve without causing displacement between the motor housing and the valve body. It is also necessary to prevent accidental separation occurring between the valve and the actuator.
In this regard, the aforementioned U.S. Pat. application Ser. No. 08/012,935 discloses a powered actuator with a bracket fixed to the motor housing and extending to a distal end which defines a generally C-shaped portion which can be fitted down over the valve body in a direction parallel to the motor axis into a coupling relationship with the valve substantially nonrotatable relative thereto about the axis of the valve stem. An actuator mechanism fixed to the motor output shaft has legs engageable in recesses in the valve handwheel for rotation thereof by the motor and hooks which fit around the edge of the handwheel to prevent movement of the actuator out of driving engagement with the handwheel.
A disadvantage of this prior arrangement is that, in order to secure the actuator to the handwheel and in order to remove it from the handwheel, it is necessary for an operator to manually set or release the hooks relative to the handwheel. This interjection of the operator's hands in close proximity to the rotating parts of the mechanism can be quite dangerous and could result in injury if the mechanism suddenly automatically starts to operate, as can occur in automatic emergency shutdown situations. Also, in this prior arrangement, the actuator mechanism and the handwheel are fully exposed in use, so that they are susceptible to inadvertent introduction of an operator's hands into close proximity with the rotating mechanism.